Such tuyeres are provided with a water jacket for cooling purposes. At one time, the water jacket consisted of a single chamber, but in more recent times separate cooling has been provided for the nose of the tuyere, either by means of a pipe for cooling water embedded in the nose or by means of a separate chamber in front of the main chamber of the tuyere.
In use a tuyere is located more or less horizontally through the wall of the blast furnace, and there is often a demand for all the tubes for cooling water to be located at the upper part of the rear of the tuyere between the 10 o'clock and 2 o'clock positions. This offers no particular difficulty as regards the water supply to the nose of the tuyere, where such a separate supply is provided, as is usually the case, but there is some difficulty in getting a good circulation of water at the front end (i.e. the nose end) of the main chamber at the 12 o'clock position.
Furthermore, the pipework in many furnaces is alternately left hand and right hand for each tuyere around the furnace so that ideally the inlet and outlet to the nose (if separately cooled) and the inlet and outlet to the main chamber should be reversible. There is no problem in doing this on the nose circuit, if it is simply a loop of tube, but it is impossible for the present designs to obtain good circulation in the main chamber at the 12 o'clock position when the water flow is reversed.